| Summary: | Organic ultraviolet (UV) phototransistors are promising for diverse applications. However, wide-bandgap organic semiconductors (OSCs) with intense UV absorption tend to exhibit large contact resistance (<i>R</i><sub>c</sub>) because of an energy-level mismatch with metal electrodes. Herein, we discovered that the molecular dopant of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F<sub>4</sub>TCNQ) was more efficient than the transition metal oxide dopant of MoO<sub>3</sub> in doping a wide-bandgap OSC, although the former showed smaller electron affinity (EA). By efficient contact doping, a low <i>R</i><sub>c</sub> of 889 Ω·cm and a high mobility of 13.89 cm<sup>2</sup>V<sup>−1</sup>s<sup>−1</sup> were achieved. As a result, UV-sensitive phototransistors showed high photosensitivity and responsivity.
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